A HMD was intended mainly for military applications when it was first introduced. With the advancement of the technology, reduced manufacturing cost, lightweight and compact structure of key components such as display, gyroscope, spatial sensor, the HMD has been extended to the consumer level for virtual reality (VR), augmented reality (AR), and mixed reality (MR) that offer visual enjoyment as compared to conventional display systems. For example, virtual reality creates an illusion of reality with images, sounds, and other sensations that replicate a real environment or an imaginary setting through the use of pairs of images provided by a near-eye display along with a gyroscope and a motion sensor. A virtual reality environment would offer a user immersion, navigation, and manipulation that simulate his physical presence in the real world or imaginary world.
Conventional approaches to locate a motion sensing equipment in a VR system would mainly be an outside-in tracking or inside-out tracking, where infrared LED elements or along with cameras are used for tracking and locating in a fixed space. However, the two approaches would require high hardware cost. Moreover, the setup would be highly difficult, and the spatial locating procedure would be complicated.